A method for assigning a geographical position to a picture is disclosed in Chinese Patent Doc. No. CN20111099180. This patent application discloses recording positional information in a picture taken by a mobile phone. The method includes the steps of starting a Global Positioning System (GPS) module of the mobile phone to obtain the positional information, saving the positional information into a memory of the mobile phone, and stopping the GPS module. When the mobile phone takes the picture, the positional information may be recalled from the memory and recorded into the picture, saving them together. In another embodiment, a picture or a picture folder in the mobile phone is browsed and a function for writing positional information may be recalled, to write the positional information into a selected picture. Also in this case, the selected picture is saved with the positional information.
More particularly, the GPS mobile phone of Chinese Patent Doc. No. CN102164345 runs the GPS module for a short time. The GPS module is not started after the picture is taken for energy conservation purposes. The positional information is written into the picture when the picture is viewed afterwards, even if the positional information is not recorded in the picture, when it is taken.
This method may have some drawbacks. First of all, the positional information acquired in a certain geographical location may be assigned to a picture which is taken in a different geographical location. Thus, the picture may be deprived of any documental value, since the positional information saved with it does not guarantee that the picture has been really taken in the geographical location indicated by the positional information.
Moreover, it may not be possible to determine the device used to take the picture from the picture and the positional information saved. This is a limitation which may further weaken the documental value of the picture. Besides, it may be difficult to identify the user taking the picture at the geographical location or to associate a date/time to the picture for proving that the device and/or the user were in a certain geographical location at a certain date/time, when the picture was taken.
Above all, there may be no way to avoid a combination of such information, for example, saving a picture in association with a date/time different from the date/time when the picture was taken or with user and/or device identification information not corresponding to an identity of the user or device really used for taking the picture.
Finally, the typical method may be limited in the precision of the positional information returned by the GPS module, especially if such module receives a weak signal, for example, due to shielded fields, delayed paths, reflections from buildings, ceilings, tunnels, etc. Of course, assigning a wrong positional information to the picture may further weaken its documental value.
Another approach for assigning a geographical position may provide that a GPS module is always active in a device, which further includes a camera for taking a picture. Substantially, this method may suffer from all the disadvantages discussed above and also from the high power consumption of the GPS module, which is always active, even when it is not necessary to retrieve a geographical position to be associated to the picture.